The invention concerns a process and an apparatus for the crystallization of melts, wherein at least one wall coolable to a temperature below the crystallization point of the melt is provided, the wall being in contact with the melt so that crystallization takes place on it.
Processes and apparatus are known (e.g., see Swiss Patent 501,421) wherein crystals are formed by the extraction of heat from the melt of a chemical product. In the known processes and apparatuses, tubular crystallizers are used, wherein a melt and a coolant run down along internal and external walls thereof, respectively, in the form of trickling films, so that the desired crystallization takes place. The crystallization is induced for the purpose of solidifying a melt or purifying a chemical product.
The purifying process is based upon the fact that crystals are purer than the initial melt. Thus, by carrying out the above-described crystallizing process, impurities can be pressured against the grain boundaries upon the formation of crystals, so that the impurities remain in the residual melt. The known processes and configurations operate discontinuously. Initially, the melt is caused to crystallize on the cooled walls of the crystallizers. Afterwards, the crystalline layer is melted and runs down the walls.
It is an object of the present invention to develop a process and an apparatus of the above-mentioned type so that it is no longer necessary to work discontinuously, but rather so that a continuous recovery of the crystallized product is possible.